CUTICULAR PROTEINS FROM 5TH INSTAR NYMPHS OF THE MIGRATORY LOCUST, LOCUSTA-MIGRATORIA

The urea-extractable proteins in cuticular samples from fifth instar nymphs of the migratory locust, Locusta migratoria, have been mapped by two-dimensional gel-electrophoresis. Extracts of samples from four different cuticular regions were analysed: hindleg femur, thoracic sterna, wing pads, and abdominal sterna plus terga. Samples were obtained both from pharate nymphal cuticle (presumptive exocuticular proteins) and from mid-instar nymphal cuticle (endocuticular proteins), and they were compared with samples from the corresponding regions of pharate and mature adult locusts. Pronounced differences were observed between corresponding samples of nymphal pharate and mid-instar cuticle. The differences between the various regions from nymphs of the same age (either pharate or mid-instar) were less pronounced, and only minor differences were observed between nymphal and adult pharate cuticles. The protein patterns from mid-instar nymphal cuticles were clearly different from the patterns from corresponding regions of adult mature cuticle, indicating a different composition and/or degree of sclerotization between the two types of endocuticle. Amino acid compositions were obtained for 15 proteins from nymphal mid-instar cuticle. They show resemblances both to proteins from adult pharate cuticle and from adult mature cuticle (endocuticle). Some of the nymphal proteins have identical amino acid compositions although they migrate to separate positions on the two-dimensional gels, indicating that they may represent single proteins modified to different degrees by post-translational modifications.